Virus scan results

After performing a scan the log showed a large number of files couldn't be opened because of errors or damaged archives. Is this a limitation of the software? Could the files that aren't scanned because of these circumstances be threats to the PC?

Windows uses certain files from the moment it starts until shutting down. Any file in use or 'open' can't be used or tampered with by any other application. When NOD32 comes across a file it's supposed to scan but can't it will make note of it. This is normal and you'll see it every time you run a scan.

Other AV's can't scan these files either. Some may fail to mention it.